Telephone apparatus and system



E. A. MELLINGER. l TELEPHONE APPARATUS AND SYSTEM.

APPLICATION man MAR.26,1901. RENEwED JUNE :31919.

Patented Feb. 8, 1920 5 SHEETS-HEET l.

E. A. MELLINGER.

TELEPHONE APPARATUS AND SYSTEM.

APPLICATION FILED MAH. 26. 1907. nENEwE1uNE. 1919.

Patented Feb. 3,1920.

5 SHEETS-SHEET 2 E. A. MELLINGER.

TELEPHGNE APPARATUS AND SYSTEM.

mmc/111011111511 1111111.26. 1907. RENEwED JUNE 5.1919.

Pantedeb. 3,1920.

5 SHEETb-SHEET 3 6@ W w@ www u VW .www dw hw@ SN@ W Q E. A. MELLINGER.

TELEPHONE APPARATUS AND SYSTEM.

APPLICATION man MAR.26,1901. RENEwED1uAE5.1919.

1330046' Patented Feb. 3,1920.

/37 5 SHEETS-Smm 4.

IIAIIII Hlll f, T3' @.W.

E. A. NIELLINGER.

TELEPHONE APPARATUS AND SYSTEM.

APPLICATION FILED MAR.26, i907. RENEWED JUNE 5. 1919.

Patented Feb. 3,1920.

5 SHEETS-SHEEI 5.

UNTTED sTnTEs PATENT oEEToE.

EDWARD A. MELLINGER, OF CHICAGO, ILLINOIS, ASSIGNOR, BY TO AUTOMATIC ELECTRIC COMPANY, A CORPORATION lMES-NE ASSIGNMENTS, or ILLINOIS. l

TELEPHONE APPARATUS AND SYSTEM.

Application led March 28, 1907, Serial No. 364,698.

To all whom t may concern Be it known that I, EDWARD A. MELLiN GER, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful Improvement in Telephone Apparatus and Systems, ot which the following is a specification.

My invention relates to telephone systems in general, but more particularly to automatic or seini-automatic telephone exchange systems, and especially to systems in ivhich electrically-propelled and step-by-step-actuated switching machines are employed for extending connection in the direction of the called subscriber. In systems ofthis kind thecalling subscriber controls lthe exchange apparatus by transmitting electrical impulses over his line, and the distance be tween the subscribers. station and one or more of the automatic switches is often such that it becomes dinieult to effectively transmit impulses over the entire length of the circuit. For this reason repeaters are sometimes employed for relaying the electrical impulses from one section of the circuit to another, so that the impulses Which are received by one or more of the switches are not transmitted over the entire length of the circuit, but are simply transmitted over a section of the circuit by one or more relays in a repeater. Repeaters for this purpose are employed, for example, in district telephone systems-that is to say, systems in which a main or central exchange is connected with a plurality of sub-central or outlying stations, which latter are in turn directly connected with the subscribers stations. In a district system of this kind it has been customary to locate the subscribers line or individual switches and the connector switches at the sub-central or outlying stations, and to locate the selectors at the exchange or main station. Also, in such systems it has been the practice to provide the connectors at the sub-central stations with ringer relays for bridginga source of ringing current across the called subscribers lines, thus necessitating special connections from the main or central station to the subcentral stations for supplying ringing current to the called subscribers lines. Furthermore, in systems ot this kind selectors have been used t'or selecting idle trunks containing repeaters, or containing repeater re- Specilcaton of Letters Patent.

Patented Feb. 3, 1920. Renewed .Tune 5,' 1919. Serial No. 301,987.

lays, and this, of course, tended toward an increase of apparatus. Again, it was very often desirable to supply the subscribers with talking current derived from a common battery at the main or central station, and this further added tothe expense and colnplication by necessitating connections for feeding talking current through the con nectors at the sub-central stations, said connectors being automatic switches by Which the final connections are completeddirectly with the called subsc1'ibe1s-lines.l vln'my improved systennhowever, I concentrate as much of the apparatus asis possible atrthe main or central station-that is -to say', I provide an arrangement :which tendstoward a greater concentrationy ofthe-apparatus at the inain `or central Vstation than heretofore. For example, I provide selectorslwliich com'- bine the'functionsof trunk selectors and repeaters and connectors, inasmuch'as eachv of these novel'selectors is provided with relays which can be employed for controlling the selector to seize an idle trunk line, which can then be employed for relaying or repeating electrical impulses to the next switch, and which can afterward be usedjfor bridging a source ofringing currentacross the circuit to supply ringing current to the called subscribers station. In this Way the same relays are not only used for extending a trunk connection from the calling subscribers line in the direction of the called subscriber, but are also then used forrepeating switch-operating impulses Ito the next switch, so that the selector thus constructed combines the functions of a trunking switch with those of a repeater. Furthermore, the selector thus equippedmakes it unnecessary to provide the connectors at the sub-central stations with ringer relays, or with any other apparatus for ringing or signaling purposes, as the selector has an arrangement for bridgingv a source of ringing current across the circuit after the conneetor has seized the called subscribers telephone line. In addition, I provide the said trunk selector with means for bridging a source of talking current across the circuit., after the latter has been completed by the seizure of the called subscribers line by thc connector, and by the taking down of the receiver at the called subscribers station. IV ith this arrangement the apparatus at the sub-central stitions can be of an exceedingly simple character, the greater part of the apparatus being concentrated at the main or central station, in the manner explained. My improved selectors have various functions when used for extending connections. For example, a calling subscriber first uses one of said selectors as a means for seizing an idle trunk line, then employs the relays of the selector for transmitting or repeating electrical impulses to the next switch, then uses-one or more ot the relays inthe selector for bridging aI source-'of ringing current across thev circuit, and finally the called subscriber uses the said selectorthat istof say, certain relays'thereofe-tor bridging a source of talking current across the said circuit. In this Way the apparatus at the lsubcentralor outlying stations is. employed for performing only connecting and releasin operations, as will hereinafter more fully appear.

In the accompanying draw-ings, Figure l shows diagrannnatically a section of the mainy exchange comprising my combination svvitchfA, aV subscribesiine switclrB, a subscribersste/tion C, and a master switch Dy for. controlling` the selective opera-tions of the line switch B and of, all other Aline sW-itches'in the same group Fig 2V is a similar View showing a subcentralstation comprising a-.modiied connector s Witch'E, a called subscribe1"s sta@ tion C', and aline switch X for the called telephone line.

Figs. land 2 taken together represent the circuits of anestablished connection between1-thesubstation; C and; the substation C', in which my xcombination switch A and the modiedv connector E are involved.

As thus illustrated the ma-inexchange is provided With the battery B having its positive terminal preferably grounded at G and the sub-excha`nge is shown provided with a battery B2 having its positive terminal preferably grounded at G2.

Fig. 3 Shows moreclearly, in a diagrammatic manner, the line switchz B and the master switch and the. connections between them.

Fig. 3a is a View of the master switch bank-K. Y

Fig. 4. is a diagrammatic perspective view of my improved Icombination switch A, showing the mechanism and circuits pertaining thereto.

F igb 5 is a similafr view of sWitchE.

In detail the switches and devices ineluded in the system comprise the following elements.

The-substation shown in Fig. 1, which may be of any suit-able or approved type, comprises a receiver 2 anda switch-hook 3, which latter has radiating from its body a number of camarms 4, 5 and 6, said hook being the modified pivotallli,vv secured to the keyboard trame (not shown) by u screw 7. In its up and down movements the switch-hook controls certain hereinafter described circuit connections. Furthermore, said substation has a transmitter S, a. ringer 9, an induction-coil l0 having` a primary Winding 11 and a secondary Winding l2, a condenser 13, and impulse wheel lll which has the usual vertical impulse teeth l5 for operating the vertical impulse spring- 1G. In addition, the impulse wheel carries a rotary impulse tooth 17 which operates the rotary impulse spring 1S. The cam-arm l controls the socalled locking arm 19 in such a manner that when the switchfhook rises and before the dial is rotated the insulating tip Q0 (upon the end of the locking cam-arm 19, that normally rests in-the position shownat substation C) is driven to the inner edge of the angled section of the ground spring 21, whereby when the dial .is rotated by the calling subscriber the pin 22 upon the end of the locking dog 23 is able to pass beneath the loc-loing cam to raise the said cam a trifle,` causing thc'said insulating tip 20 to tall behind the said angled section of the ground spring Q1, and permitting-the said spring to make cgntact with a -coperating ground spring 2l and Q4 p aces thel ground post 25 in oonnection with the substation ground G3, whereby, when the subscriber releases the dial, the vertical impulse teeth l5 (by causingthe vertical impulse spring 1G to come in contact with the same ground post 25) sends ground impulses over the subscriber`s vertical line conductor to the centr-al otlice'; and immediately following, the rotary impulse tooth 1T (by causing the rotary impulse spring 1S to come in contact with the same ground post sends a ground impulse over the :rotary conductor. Then the switch-hook is down the cam-arm 6 maintains the sWitchsprin-gs 26 and E27 in oontaict, thereby1 bridging the ringer 9 in series with the condenser 13 across the line. The springs 28 and 29 are then disengaged, and the primary Winding 11 in series with the transmitter 8 is removed from across the line. Even after the switch-hook is raised, and since the finger 30 of the cam-dog 23 controls the engagement of the said springs Q8 and 29, and since .the said ca1n-dog rotates in unison with the dial, if the dial is rotated the springs 28 and 29, and, therelore-` the subscribers line conductors are kept separated during said rotation. The sig'- naling device whereby a subscriber may signal another after a connect-ion has been es-` v tablished comprises a push-button 3l and spring 32, which latter normally engages the contact point 33; but when the push-'button 3l is pressed the spring 32 leaves the contact point 33 andengages the Contact point 34 The engagement ot' the ground springs which is connected to the substation ground G3. The means whereby the subscriber may release the central station apparatus brought into service comprises three springs 35, 36 and 37 (commonly known as release springs) so controlled by the cam-arm 5 that when the switch-hook descends the release springs are brought into contact, thereby grounding both sides of the subscribers line simultaneously. The said cam-arm 5 is provided with a lateral flange 38 that is adapted to engage `a corresponding lateral flange 39 upon the release spring 37; and as the switchhook descends, the said flanges 38 and 39 so force the said spring 37 as to crowd the three release springs into electrical contact. lVhen the switch-hook rises, however, the flange 3S engages the flange 39 on the opposite side, so that the spring 37 is not pressed onto the sprin 36 at the upward motion of the switch-hoo A somewhat similar provision is made for the vertical and rotary impulse springs 16 and 18; the former is provided with a flange 40a which is engaged byl the vertical impulse teeth l5, and the latter (namely. the rotary impulse spring 18)#is provided with a corresponding flange 40 which is engaged by the rotary yimpulse toothV 17. Furthermore, the switch-hook 3 is provided with a fourth cam member 38aL which, as the' switch-hook rises, momentarily engages the spring 39, whereby a preliminary ground impulse is transmitted to the rot-ary line conductor for operating the line switch B. It will be noticed that the part of the switch-hook bearing the cam member 38a is separated from the partbearing the cam-arms 4, 5 and 6 by the insulating pieec 37a.

The line switch B may be of any suitable or approved type. Said line switch is built upon a suitable irame `and comprises a plunger ell and a plunger arm 42. t is also equipped with a cut-off relay i3 and trip magnet il and the switch release magnet 45. The said magnets may be secured to the switch frame by any means known to the art. The said release magnet l5 is provided with an armature 4:6 that is pivoted to a pin 47, the latter rising from the Jframe of the switch. This armature is normally held away from the pole-pieces of the magnet-by a suitable spring 48. The said armature 46 carries pivotally secured to its end a second armature i9 that is controlled by the trip magnet el and which is normali)Y held away from the pole-pieces of the said trip magnet by a suitable spring 50. The pin 5l about which the armature i9 oscillates is, of course, carried on a bifurcated terminal et the armature #16. The plunger ll is pivotally secured by a pin to the plunger arm i2, which latter is in turn pivotally held in place by a pin 53. The said line switch provided with a bank of terminals, usually ten in number but only one ot' which is shown at J. As shown in F ig. 3, and for convenience of illustration, the said tern'iinal J is turned or twisted from its true position with respect to the swing of the plunger 4l. The terminal J comprises the springs 54: and 55, 56 and 57, 58 and 59, and 60 and 61. The said springs are normally disconnected from each other, but may be driven into contact when the plunger ll-operates,'in .the following order: and 55, 56 andv57, 58 and 59, and'GO and G1. Normally the plunger 4l is, however, retained out of engagement with the line switch bank and in engagement with the pllinger-controlling shaft 62, which latter is operated by the master switch D. The said plunger is thus held Iby the armature 49 of the trip magnet 4l., which latter is provided with a terminal 63 adapted to engage the rear terminal Gl of the plunger arm 42. The cut-ofi" relay 43 is provided with springs 6G, 67 and 67 for controlling the energizing circuit of thetrip magnet all. The operation oflthe lineswitch B in general is as followszVhen the subscriber removes his receiver 2 from theswitch-hook 3, the latter lupon vrising sends a preliminary impulse tothe 'central office and energizes the trip magnet all for the moment, whereby the armature 49 is at'tractedand the catch 63 is disengaged from the plunger arm ai?. Then a spring 65 rotates the said arm Je? about the pin 53, and if the position of the plunger shaft 62 is such that the plunger 5l isopposite the terminal J, the said plunger il `is then thrust between the terminal springs 60 and 54, whereby the said terminal springs are closed intocontact with their mate springs, as already de-A scribed. The plunger shaft 62 is provided with a longitudinal channel 78 in which the upper ends ot' the plungers normally rest. lVhen a plunger is brought to rest it is restored by the` momentary energization of the release magnet l5, which release occurs when the subscriber hangs up vhis receiver and grounds both of his line conductors simultaneously. lVhen thus energized the release magnet attracts the release armature 4G, whereby the armature 49 of the trip magnet 44 is raised sufiiciently to permit the catch terminal G3 to drop into normal engagen'ient with the plunger arm i2. Then when the release magnet denergizes the plunger 41 is drawn from the bank and carried into engagement with the shaft 62. It will be understood that the plunger shaft has an oscillatory motion, and at no time does the channel 'T8 pass out of the range of the rear or upper end 78a of the plunger il.

The master switch D is provided for operating the plunger shaft 62 and for controlling certain circuits which will be disclosed.

lt is a comparatively simple switch, having the following details: a motor magnet .69 for operating the ratchet `Wheel 70, which latter'fin-tuin controls the lungcr shaft'z. llhefswitch also has a 'diiiirential aelay 7l and an .auxiliary relay 72, the former controlling the energizing circuit-df the motor magnet i69, and the latter the energizing circuit of :all wtrip :magnets '44: of theline switches fcontrolled by said nnaster switch. Bhe @said llnaster switch also has :a bank K comprising .a plurality -of .individual contact .segments a., yand .a fmetallic segment 73 commen to'the said segments @,fas shown in lig. .3. The Awiper 74 is adaptedto remain in constant Aengagement; with the bank "K'to maintain atfall times some one of the segments .a in electr-ical connection :with the common segment 73,.except when the wiper Tapasses :from the iextrenie left contact'to the -textreme right contact, as will 'be more fully explained. The .wiper 74: .is operated in :a step by -step manner by the yratchet wheel .-70, 4through the medium of a cani member 75 aigidly vsecured to the` said wiper 7-l and adapted to .sdccessively engage #the pins'76, 7, A781and '79 upon'the'said :ratchet wheel .70. The :motor magnet 69 is :provided witlran:armature'm'8L alpen the end y of --Which there Ais suitably'secnreda pawl 80. :Each time ithat :the said magnet is .energized the pawl v89 engages the ratchet :wheel l70, ad vancing the .latter one step. It Iwill be seen, therefore, that as lthe ratchet lwheel -70 advances in a forward direction the wiper 74 admnces step-by step fron1 right -to left, and that-When'ftheipin176, for example, "clears the ca1n175 fthe retracting-springSl restores the wiper 74 to Iits first -position at the 7right ot Athe bank 2K and inrengagement lwith the first segment "82. The master 4switch bank Kshown 4in Fig. 3a-comprisesithe individual Contact segments a separated -from fthe cominoirsegnient 73 by the insulating strip 73a. rPhe linsulating member 74a is :provided -so tha-tvwhenthe wiper YY1-passes -fronithe extreme lleft contact 84a tothe=extreme right contact 82, the upper part of the Wiper 74 slides-onthepiece 741,-'thus preventing the wiper arm 721 from placing the contact-seg ments@ in connection-With thefcommon segment 73, -whereby some interference might be experienced t'by the `master switch. The said "motor 1nagnet-69 is provided with an interrupter -comprising a couple 4of interrnp'ter springsSS and S4 that are included in thefenergizingcircuit of `the said motor magnet, which energizing'circuit also-comprises the 'springs A85 -and 86 controlled by the differential lrelay .71. Said interrupter may .tbe lof the general type disclosed in United States Patent No. 831.875, granted Septe11ibe125,1906, to AE. iKeith, `'for improvement in'interrupter 1for automatic telephoneor other switches. 'Therefore, Whenl1 ses ego-ic cve-r :the diierential relay 71 .is energized thef'Springs 185 and :'86 -are'pressed finto conta'ct, :and the :motor =n1agnet -:69 :operates -step by step fas 'long las f the differential .Irelay li7() remainsl energized. llt is :assumed that ithe tem'ninal'al ot'rthefline switch B -isvthciiirst terminaL ofithe fline'switchbanl. .Theaplimgerl'l'l lis fretnined f in front of said terminal bv Athegplunger shaft 62 Whenever the un aster switch fwiper 7f1'is in=engagement withdahe baiiksegment 82;*bu't as -the motor magnet G0 advances the wiper 7a -onto the Lsecond segment 37, :all :idle i plungerasare @carried 0pposite fthe rnext iterininal off I*the .'line :iswitch bunk. Itfshould be noted1that in :each Iline switchibank all oi ithesprings 60 are ipermanently .connected and maybesmade of-,one common piece. The-'springs 59,fhoave\-'er,:are

individualkethat is,'the1'e is one separate and distinct sspring .ffor every `ban-lc 'terminal J, there'be'ing, thereforeftten in @all :in itheffbanl. T'hefspiiings 58,-54: and 5G, like-the Isprings 60,1are also connnn, and ithe ssprings .'rand zrrlilethe .fsprings '59., :are individual. "For every rbanklterminaLU f there is .iartrunk iline of' .three .conductors rS-S, S9 zand 90 vleadingtto aaselector,3andzthere is also a fnormal .trunk linefcomprising the condnctors'Ql, 92iand 93 leading Ito the :connector .'banls. The-'subsorib'ers :line .conductors 914 anidv95 fterminate 9 inlthe springs .liand 5B which, as has'fbeen stated, are 'connno-n springs. Whenithe subscriber operates :the line switch B in'connection avith't-heterminal 1J the subscriber-s line conductors 294 .fand 95 are extended :to fthe vertical a nd rotaryv trunk :conductors 88 .and S9, fand .thence :to fthe :switch A.

lheselector switch A is:an:improvement on the selector switch disclosed in )United States'iatent No. 815,321, :granted March 13, 1906, to Keith, Erickson and 7Erickson, tor improvement .in v automatic :telephone selector switch. It compri-ses a switch shaft 6 8 to which are att/ached the lvertical and rotary iline wipers 96 :and 97 :and the pri vate :Wiper 9S. The said Ishaft iscontrclled by .the calling vsubscriber fthrough =the medininfof vthe lvertical .and rotar.)7 line mela-ys 99 `and .100. -Theformer isladaptedto operate the Avertical magnet vi101, which magnet is designed ito -inipartdoithe switch-shaft 68 its vertical movement The tpri-vate magnet l021is-c'ontrolled byfthe rotary linerelatv i100, said private fxnagnet having control =of 'the Wellknown side -switoh "F that comprises the-side switch-wipers 103, 104,105, 106- and 107. Whenfthe said fpri-vate -magnet l102 'is operated once,1the'side switch /passesito second position, and an 'energizing circuit is established through 'the rotary magnet '108, whereby the said 'magnet becomes operative to vrotate the switch shaft 1(58 in the Wellknown manner. The vertical and rotary line relays 99 and 100 areadapted to control the release magnet 109 when the subwith one of the'features that are disclosed in the connector switch of United States Patent No. 815,17 6, granted March 13, 1906, to Keith, Erickson and Erickson, for improvement in automatic telephone connector switch, namely a ringer relay l110. The said relay is adapted when energized, or after. a connection has been established with the desired subscribers line, to disconnect the calling subscribers line from the calledgsubscribers line, and to bridge across the latter a ringer generator 111. The said relay 110 performs the said functions through the medium of the ringer relay springs 112, 113, 114, 115 and' 116 allotted to said relay. Said switch is, furthermore, provided with a dif-v ferential relay 117 having two windings 118 and 119. Said differential relay has various functions, among which are the follow'- ing: The winding 119 being in series with the vertical line relay 99, and the winding 118 being in series with the rotary'line re-v lay 100, the said differential relay is adapt# ed to be energized whenevereitherofgsaid line relays 99 or 100 is energized. However, when thesaid line relays are Fenergized si; multaneously, in a series circuit, 'the-differential relay 117 does not energize; but whenj the said relays are energized in a multiple circuit the differential relay does energize. The said differential relay is adapted'to control the energizing circuit ofthe ringer relay 110, whereby the called subscriber may be signaled after the desired connection has been established. The said differential relay, furthermore, controls the energizing cir cuit of the release magnet 109, as will be more fully disclosed. The main talking cir cuit that passes through the switch A when two subscribers are connected is divided into two sections by the condensers 120 and 121. On the side of the calling subscriber the line relays 99 and 100 and the' differential relay 117 are bridged across the said talking circuit; and on the side of the called subscriberthere is bridged a double-wound relay 122 through which the charging or talking current is provided for the transmitter of the called subscriber when the said subscriber answers, and, of course, after the side switch wiper 105 has passed into third position and into engagement with the ground terminal. )Vhcn the called subscriber answers, the said relay 122 then encrgizes and provides the calling subscriber, in turn, with energizing current for his transmitter. For releasing, the switch has a release relay 122a which controls the release of the line switch B, as will be described. The switch A is in addition provided with aline switching relay 123 and an auxiliary relay 124, the functions of which will be fully described. f The said switch A is, of course,'provided'with line and private banks 125 and 126, respectively, which are allotted to the respective line and private wipers 96 and 97, and 98. For purposes to be disclosed, each trunk line leading from the line bank 125 is provided with a private trunk relay a which controls the auxiliary relay 124.

rlhe connector switch E is an improvement upon the one shown in the aforesaid connector switch patent. As in the said connector switch v the switch E comprises the switch shaft 127, the line wipers 128 and 129, the private wiper 130 and the line bank 131, private bank 132, the longitudinal teeth 133 on the shaft 127, circular teeth 134, the vertical magnet 135, the rotary magnet 136, private magnet 137 and the release magnet 138.A In addition there is an auxiliai-y or line relay 139 for controlling the operations of the vertical, rotary and release magnets 135, 136 and 138. The said connector switch is provided with the usual side switch G. The line switch X of the called line (Fig. 2) and the called substation C- `Ibeing identical with the line switch Band 'the substation C, furtherexplanation will not'be necessary. 'Like parts being similarly= represented in the different figures, there will 'be no 'difficulty in understanding the circuits as represented in the following: n

The operation' of the system will be more fully understood if-a description is given of the various steps which occur when one subscriber (C, Fig. 1. for example) calls another subscriber (C, Fig. 2). Assuming that the number ofthe substation C is 220, a subscriber at substation C, after removing his receiver and operating the line switch B to connect with the selector A by a preliminary impulse, as already explained, proceeds by operating his dial once for each digit of the desired number. At'the first operation of the dial, in accordance with the first digit 2, the vertical trunk conductor 88 is'grounded twice, and then the rotary trunk' conductor 89 is grounded once, whereby the vswitch A is operated to establish connection with the connector E. The second operation of the dial, in accordance with the second digit 2, causes ground impulses to be likewise sent to the rotary and `vertical trunk conductors 181 and 182 for operating the connector switch E, whereby the wipers of the said connector switch are raised to a level with a group of line terminals among which is the terminal of the desired telephone line. When the dial is operated for the last time the shaft of the connector is rotated so that' the calling subscriber-s line is carried into connection with the called-subscribers line, if the said line is not busy.

The preliminary impulse, to which reference has been made, is sent in when the subseuibeu neiuoues his reoeive1r2 from. the switch-hook and thereby.I permits,- tliearnr te. engage theground spring-394:. Thefrm tary lineeonductor. 95.is5tl1us grounded once.,

andthe .trip .magnet 44a-of the line swtelu B is.. energized-'by a flore of: current: froml the substation ground to the ground-z spring 39, tl'ieneefto the switch-hookaand tofthewconducten 'M15 and thence tothe; IQtauy" line conductor 95,'Conducto1 1.42* at the line switch 735. out-off. springs' 67; 67:1' and 66, trip magnet.' 4&5 ool'iduct/Dr '143,'. auxiliary..- relay suringsftfl; and.' ldto tllebattery lead 146, and throng-ii batters' Bt to=ground (SH. As already. explained, the trip: magnet?. attracts the armature 49,. thus, releasing the.' plunger arm. di. and causing the plunger. el. to be driven into the bank( terminal? 'Jj byf. the springe (la. Tilie operation; of. tl1e=plunger el establishes. ai number of circuits andi p1`0- threes, .a i numbeu of operations.- RS.: `follows: 'lilla bank .springs 5,8 andi 59 fbeingi pressed into :Contant-a guanllngf potentiallrslestab lishedl. at@ the .masten sait-ela baule contact. 8B for' operatil'ig the; master"v sxvitiwfllhis guarding..r potential; is. established; fron-i.:v the s-aidmontact pQiDtBaOver-the 'conducten14:7v to: the bank: springl 5.9.;- theneetov the vba'nl spring 58? andwtlrough the release/.magnet 4:5 tothe liatteryylead 146.- The. gu'ardingfpotential thus established at the conticiwpnnt Sr-is negativa. and; since themaster. switoh viper is atzhe time-in engagement` With-the said Contact; 8Qfand"with.fthe commoirmembe11-734oirtheibanlfK,v an energizing eircuit isv establlshed through' the mastersmiteh auxiliiugol 'M7-2,1'anddiuougliithewinding llSoftlre diil'erentialrelay '71L. Theeurrent liowsffrom {tl1econtact point( Sr-,at'ftli'emmster switch bank ithroughlthe wiper. 7Ltrto.tle segmenti 7f3, thoube over tlxo-oendueton 14%) tothea'ui'iliargn relayi 7 il; Aand(through. said relay and .the winding.' 1480i theA di erential relaiY 7l.to the groundterminal?G4; It: will be .seeulthat this eircuitmlso includestll'e releaseuuagnet of.' the.` linefswitchi B5 but the u'indiiigsmf the relays 7'2: and 7l are' of such; resistance thati suliiient: current does noti luiv to operatively energine the release magnetd; Both the auxiliary. relay Trand the'differentiali'lelay 71 enelgize, alulf the latter, upont attracting its.' auiature; fences the springs 85y andl 861i`utov engagement; in turnestabllsliing a ciruitf through: the metor magnet GSlfrom-.groundG5 tliuough the said springs 85|and186and tlirouglrtbe nu tou magnet? 69 tIrtiie' interrupteurspring S45 thence to the inteiu'upteu spring'Sl and: to thefbatteuy.- leadl 5146, and@thmughzbattery. Bf to 1 ground G. TheI motor 'magnet 69:. upon attractingrits'. armatue 77?causes tlies paavl SOfto-.engage tlie'ratehet- Wheel 7 0', rotating tbe said Wheel one Step and eaus-ingthe wiper 7 4.1 to" leavethe: Contact'. points 82.-" and advance onto` tlieI cunt-actE pointe 87. Since' the. pluugerashaft G2i is rigidzwitlrtbe wiper es ther said shaft: 62: is also' advanced one steppwihereby allidleplungersare advanced to a; position4 opposite.A thenext' bank terminalothe: line switch. bank.. it. W-illbe evident':tl1at Wlieni the-motor vmagnet 69. attracts its f armaturer the .spizings :83 and 8l sep arate, break-ing the; energizing' circuit. for the said motor magnet, andi Whemthe Wiperv 7 4 is advanced' Onto the banlt segment 87.- the. ener- Girouiti for. the, dileiential: relay 7.1 andzonthe auzeiliauy'relajyi 7;'2fisibroken, uuless this segmentis also preteetediby aguardF ingfpotentiall lnjlliseveut die-sadoii-.cuit isi not; broker-u andi tliev difelential. relay: 7l will be retained zeuergized; .andi when the ino# tou magneti armature '77 restablislies the energizing/ennuis, for, the motor* magnet' G9 the Said?- magnet. is `energized! once: inore;.and the-wiper 7d; togetlierfuitiiithe fpluuger shaft 625.11m? adiiancedl one more y stopt This oper.. ation is; of course,.repeated aggolteu as; the Wipeu 7d finds@ protested;orrguardedl contaets. Howeveig-asrseoiuastlie wiper 7 d leaves the laste buey contanti thet de'eine'lgizaftiou'A of the differential! relayl 7l their fellows, wbeaeby. theediifnental:relayspuiugs S-faud 86 sepaLaefbefore.A thef-moton-magnet denergizes.; andlaeairesnltithe.energizing:cirouittlirough time saidwmotn1 magnet is..t1en penmanently brokeni It willbenetioedithatrtlie-tuip fmagr rieti-,4411; of: tbe line.- suwitch: isi contuolled' by the.: auxiliary.; relay 72; andi as al matter` or' fact alli'trip magnets of' theliney swdtehes controlled: by: theV masters switch. D.r are thus conneeteds. The. objeotf in thus destroying the eneigizting circuits. for the tripmagnets ofi the group! is.; tr prevent any subscriber wflio mayremove'liisdeceveu at the instant that theliuastelxswitoli TF1-'is` operating from trapping bis.' imliridi'la-l. switolr, and. causing hisfpllmgelrte seizeupeu-a busy. truuk. lim. 'llle closure of'eonneetionbetweentlie bank springs? GQ-andf'l,.wlienl the plunger L is Operated. establishes :u guarding vpotential of? agpositis'enature at the 'unina-te normal conduothr: Slrrlroini ground; Gt, wliiulr guarding; p etentiali is extended: th the connue-tor private' bla-uli wntaetse corresponding; to' tl 1e substatiwrV C.. whereby; no. subseriben \vill. be able-toduterfere withtlelineafter the subsorfber, has. bagnato make; a: call.- This guarding?,- potentali. furthermore... sends :i flow? ofcurrent: through the cutoff' uuigaxet 43'! of: the: liueswitblr B; from. ground thuoug'hf thefsl ufings'lvv and -60 'to tl le mud ur.- tor.f 1.'5O.,,the1wel through the said. eut-ofi" n.- lay 4tistfhtlle' battery' lead7 1.46, them through battery B1 'to' grvxund-r G17 Tliefenergization of; saidieuteoirmlay43aoeomplishes -tfwoobjects; namely the; removal of;-theshort-oir` euitofftheeline'eonductors 9i a-ndzQS/tlirough thmsprings and". 67afromi aeross the: sub-- seriberxs.- linee, and! the diseonneetoni ofr the trip. 4.4, mnfrl the line, so. that the llO electric impulses that are to follow will not operate to energize the saidtrip magnet 44. l-Vhen the plunger 41 presses the springs 54 and 55. into contact, and thesprings 56 and 57 linto contact, the subscribers line concluetors 94' and 95 are extended to the trunk conductors`88 and 89 and put in connection with the selector A; therefore, after the line switch B is operated as described, the succeeding impulses that come from thesubstation will-be directed to the switch The first digit being 2, when the subscriber Operates his dial he grounds the vertical line conductor 94-twice, each time energizing the vertical line .relay 99 ot' the selector A, and at the same time the diferential relay 117. The operating current passes from the substation ground G3 through the ground springs 21-and 24 to the groundpost 25, thence through the vertical impulseA spring 16 to the vertical line conductor 94, line switch bank springs 54 and 55 to the verti# cal trunkconductor 88 and to the.. vertical line relay 99, thence through said relay and through the winding 119 of the dierential relay 117y to the battery lead 146,-"thence through -battery B to ground G. "The-ens ergization of the Idiierential -relay is of no consequence at this time, but the' vertical line relay,'on pressing the spring151 onto the ground spring 152, sends a flow otcurrent through the vertical magnet 101 for raising the' switch shaft 68. Since thesaid relay 99 operates twice, the vertical magnet 101 is energized twice, attracting 'its armature 153, which armature operatesto raise the shaft 68 two steps, thus placing the line wipers 96 and 97 and the private wiper 98 opposite the irst Contact of the second level of the line and private banks 125 and 126. The current that passes through the vertical magnet 101 flows from the ground terminal G7 through the springs 152 and 151, conductor 154, line switching relay, springs 196 and 198, conductor 157 to the private springs 158 and 159, conductor 160, sideY switch wiper 104, contacty point 161, conductor 162 to the vertical magnet 101, thence to the battery lead 146, and through battery B to ground G." The ground impulse to the rotary line conductor 95 which follows operates the rotary line relay 100 at the selector A, together with the differential relay 117.

The operation of the latter relay is still of l .no consequence. The current flows troni the` substation ground Gr3 to the ground post'25, thence to the rotary impulse spring y18, r0- tary line conductor 95, line switch bank springs '56 and 57 to the rotary trunk conduct-or 89, thence to thev rotary line relay 100 and through the said relay and winding 118 ofthe dierential relay 117 to the conductor 163, back-bridge relay springs 164 and 165 to the battery lead 146, thence through battery B -to ground G. The

rotary line relay 100, uponA energizing, carries'the spring 166 into engagementrwith the ground` spring 152, thereby sendingan impulse to the private magnet l102 foroperating the side switch F. The energizingcurrent passes from ground G7 through the vsprings 152 and 166, through the `li-neswitching re-.

lay springs 197 `Iand 199` conductor 169. to the private magnet 102,- thencethrough said magnet tothe conductor -17 0, back-bridge relay springs 164- and -165-tothe battery lead 146,.thence through battery-,B: to ground G. The: private magnet 1023energiz'es Land denergizes, and in so' doing- .permits the side switch arm 171-topassfrom first-f to second position, lin the Awell-known manner. The side switch wiper103,therefore passes intoengagement with thecontact point 172, establishing an energizing: circuit tor the rotary magnet 10.8 from-ground- Gr8 through the .side switch wiper 103 to the 'contact point 172, rotary magnet 108 and :inter-I rupter springs 173rto'theaybattery llead'146, thence through i battery. nto f ground G-, The rotary. magnet "108g energizesy therefore, and l attracts-f its 'armatulre 2174,'.- rotati'ng fthe shafty :68 soi as to` carry the.l line-zwipers l96 and 97 and? the. :private iwiper A'-98 into en; gageme'nt with the -rst-contact of the second level of! the .line-and privatefbanks; If .the rst trunk line' leadingtherefrom.'is'busy, as iswell known the 'private wiper 98v finds a grounded .contact which provides potential for renergizing the privatewmagnet--102, whereby-the side :switch -F is locked lin secondl position; therefore,v the side Switch wiper-103 is maintained iii-engagement with the contact point 172 until thewipers are rotated into engagement-with some idle trunk line, at which time the energizing'circuit through the private magnet 102 is broken and theisideswitchpas'ses -to-third. position, permanently :destroying the energif/Jing circuit' for the-rotary magnet 108. It will be understood that when the rotary magnetl 108 energizes in the-first instance, as described, 'the' rotary armature linger 175 engages the private .armature 176 and operates the latter so that the private-sprinfrs 17 7 and 178 are carried into,- contact. ft the private wiper 98, as has been suggested, finds agronnded contact, a low` of currentlpasses through the' said private magnet from the grounded contactto the `private wiper 98, thence through the auxiliary-relay A124 t0 the side switch4 wiper 105, contact point 179` conductor 180, private lsprings 178 and 177 to the private magnet 102, thence to the con! ductor 170 and back-bridge relay springs 164 and 165v to the battery`v lead 146, and through battery B to ground G. The private magnet 102, upon energizing, with-A holds the armature 176 from the rotary armaturefinger 175 as the rotary armature 174 recedes, thus locking itselfin an energizing; eirouit-:untiltthe said e1iergizing.-l oir-4 ouit:isfinteiruptedpwihen the private; Wiper 98'. leaves! thex lastlgmunded contact: point: fieourse, .Whilefthefside switch .is thus .lheld in:second.zposition,I .n.-ndas oftenesfthe armata ture' 1.74: falls: hack' andA the. interrupter springs-173'1zirefpermitted.to eng-nge, the :said mtery. magneti is-zigaiin energized', ,aindithereA foie the shaft: 68.' ie vrotiiteciistepihy-step but when tli'erpriviutwiperf 98: is `advanced .until the energizingsoirouit fon the' private magnet1102. isiinterrupted, tlielprivnte' armature liffnlls fbzwle tothe oaresof the-rotary urina ture fiirger'l, soithat Whenthe armature 1741. returns: tonormel. position there side. switohfF escapessto .third positioneheforethe rotary magnet: 108.\'hzis-ti1ne.A to i again! enerih gi'ze. Ifitheiisb trunkis notrbusy, however', the rot-ary ennnturefl'lgnt the first' stroke,- operzttee tlef private armaturei 17 (ftiirough theinedium of the rotary armature fingen 175,50 that the sidefswitohilir escapes from secondi to third: positionVin the usuiilzand well-known manner. It! will befnotieedtlmt' while-the private Wiper-i 98` istmxf'elingr over groundedcontaets, 4the energining.' circuit vltor. the private magnet 102` passee: through'. the. uuxilinir7 relay124:;but'thesaidrreliy 1241 iswound lto a very low' resistance,I while: the. private magneti 102' is of.' suieiently: high resistztnoeito' out! dow-n1 the iiow ofi current' so that? the relayf 1241:v cannot. operatively` energize; Any-r suitables resistancee mary, of: oourse,. be given tothe` coil' 124i; hutf. it has been found: that good results- :rreobtained Withzr. resistance otl onehulf ohm; Assum ing-that? the: wipers are rote-ted' and. carried' into engagementwith the trunlrA lne=leznling from thetentii terminali ot' the second'- level ot' theba1ilcs,1.then wlien the side.- switch: F' passesl to thirdf. position f. the suhsoribers line eondiiotors` 94* and 95 (which, by. the operak tion Ofit'he line4l switch B; were" connected with the.' trunkz conductors 88'n sind" 89)v :ire extended' to'= thel trunk conduotors--181a and 182.' over :ri eirouit Whioh'. ist temporarily. opened! by the -energization ofi tlie' auxiliaryreleyi12ft', Wiiioh letter! energizeens soon" zustlie sideswiteha passesto' third' position'7 breaking the oonneetionolrzone Side;1zi'nd.the seid'. relay.' 124' in` turn: causes the energizael ti on.' of the' lino Switehing relay 123, which hitter.` lnfewls the connection on: the' other side.: TheenergizingT oirouitf Jfor tlie Seid :iuxiliry relay 1242 extendl from the` side lvite-ln ground@ G9 to i'vlie'oonta-.et point: 188, eide switoli. wiperlO: oonduotor 184; auxiliaryf relay- 124: to: theI private wiper' 98, privater trunk@ relay.' springs 185 and 186, rel eistunc'e coil1187ftotliebattery lead 1216; and through Battery-B. to ground-Gf. Themuxe ilia ry inlay-"124; .upon energizing, .ehifts the Spring 188 :www from the' spring: 1892 and intoengngement with; thefspring 19.0, and the spring." 191e into-1 engagementwith' the igsaopeo spring-'192:- Whenthesprings 191 @M1192 engagegen energiiingroireuitis then estab lishedithrongh l.the-line switching relay 123 from. ground- Gdl through. the: seid' springs 1911 and 192, conductor. 193to the=relay123, thence through. seid: relay to the-battery le1tdI11,\.and through hatte-1y B" toigronnd Gf; The4- sii-idf relay.' 123, upon'. energizing; shifts; the spring 1941. away from: tlie spr-ing 195,- and thesprings 19.6fend 197: aweyi from the springs'- 198211161 199; respectively, and into'.I enge-gement: With'. thex springe: 195xx amd 206; By.' studying: the.: combinedi :motion: of.

the relays: 124i-2nndi128it will ihe notice-ol tha-tthezspringf189P off the auxiliary: relay 124 constitutes therv terminalz'ofl' the trunk; con; dnetonlSlg. and? that the springf 195` of the lineswitching relay 123 constitutes: the terminal otthe' vertice-l ltrnnkl:oonductm.182 Furthermore, Wlienthef said' springs- `189l land 195.'` lezrve'` tliieiii4 xeepeotivel Springe` 1883 and 194; connection i'sibrolenihetweeni the :trunkoondueto rs 181" and'. 182 amdl the snlieoribels extended. line; conductors.. 881and? 89;. as alreally' Sttvtedi. The=spring120 of? theoline switching.l relxy: 123; it' willi lie seen; .isx also conneeted. permanently with:4 the rotary trunk oonduetori 18'11";- Ini additicmg. the springs 197i and 196of'the linel switching relay 123i aref. direotlyv connected. with the springs 151 andi 166% oftlie Vertical. and rotar-yf line' relaye 99.' ztud- 1001;; therefno,` whenfthe-flineswittliingfrelay 123-mnd1 aux-v iliary' relay.` 124s eni-znqgiiz'e,` thex tl'nnll con'- ductm-sz1821andf181 are' sere-radi fmm the trunk oonduotnrs 88'- :m'd: 89,. and the line relixy springeV 11.. andz 166e are. diiseonnected from.' the internelxoirouits of the sWitehA' and: placed? directly: in. connection. with the trimki' oonduotorsf: 182" :md 181,. whereby, when' the' linel relaiye- 99'arnd1 10G) :tre oneretedi after Athesidef switel'it E passes-z to', third position, kthe impul seW'ill ibeerepezntedto' the trunle; conductors 1821' zuid 181;. fn'operzrttingtthe oonnectonswiteli E.' Euithermore', When'the 'side switch- El passes .tb thirdi posif tion the' seized trnnlnl line` ire-protected hy the' gnandingrpotential tirait( appeal@ et' the priva-te Wiperl 98;..thrm1ghi the' auxiliary rehw 124,,asfis-ueuallyfthe ease. 'llie private. Wi per QS-heingninengztgement: .with the-tenth oontaotr. ofv the second'. levell ofi the private bank 126,- oonneotitui'is.- thereby established with .theprivate trunk-1 conductor,- 181*lx that. extends to the eoinieetnr: E, and: throucrh' whielnth e releasing otr the oonneetor. E teliee plzioet :titer the Subsc'.rfibei'sl :ire through talking:

TheT secondi di,r ;itf.v being 2, the subscriber again operates-:his dia tgroundthewertiwl lineioonduotoi=94+twice,- each itim eieiergi'zingr the vertical line relay 99,:-01'2 the: selector Ai over oirouits thatfnree airedyxknown.. 'Bhe safidi relay, upon; pressing the' springs 15:1; and 152' into.- oontect, .new repeatsi impulses to the vertical trunk conductor 182 that leads to the connector E, for energizing the line relay 139 at they said connector. The energizing circuit for the'said relay 139 may be traced` from ground G7 through the Asprings 152 and 151- to the conductor 154,

thence, through the` line 'switching relay springs 196-and'1955to the conductor 201, vertical'line wiperl 96, vertical trunkconductor 182, side switch Wiper 202 of the side switch G at the connector E, contact point 203 to the 'relay 139, thence to battery lead 204, and through battery B? .to ground G2. Eachtime that the relay. `139 energizes, it presses the: springs 205 and 206 into lconftactfeach time c ,nergizii'igI the vertical mag- :battery IvB2 to ground G." 1 Each time that thev f vertical magnet 135 attracts its arl mature 212it raises 'the switch shaft 127 one step, as isv well known. The -grounding of the rotaryline conductor 95, that follows the 'grounding-of the vertical line conductor,

energizesthe'rotary line'relay 100, as is alreadyflrnown, over circuits that have beenv described'. Said relay again presses the springs 166 land 152 into contact, thereby grounding the rotary trunk conductor 181, and as a result operating the private magnet 137 of the connector E. The current through the said private magnet flows from ground G7 through the springs 152 and 166 to the line switching relaysprings 197 and 200, thence to the conductor 213 and to the rotary wiper 97, rotary trunk conductor 181, side switch, wiper 214 ofthe connector E, contact point 215 to the private magnet 137, thenceto the battery lead 204, and through battery B2 to `ground G2. 'As is well known, the private magnet energizes and denergizes, permitting the side switch G to pass to second position. Therefore, since the side switch wiper 211 shifts into engagement with the contact point 216, when the relay 139 next operates, the rotary magnet 136 responds instead of the vertical magnet 135,

Thevthird digit 'being naught the subf scriber operates his dial accordingly, grounding the vertical line conductor 94 ten times, and operating the vertical .line relay 99 ten times, and again grounding the lvertical trunk conductor 182 each time the said relay 99 is energized. The vertical trunk conductor `182 being grounded ten times, the line relay 139 at the connector E is energized ten times, and the springs 205 and 206 are pressed into contact each time. The

lmagnet 137, upon operating, sends, the side rotary magnet 136 is thus operated to rotate the -shaft 127 ten steps, carrying the line wipers 128 and 129 into engagement with the normal conductors 217 and 218 that lead `throughpthe called subscribers line switch X to tliecalled subscribers'station #220; and the private wiper 130 is carried-'into engagement with the private normal conductor 219 that terminates in the said line switch X. When the subscriber grounds his rotary line conductor for the last time he operates the rotary line relay at the selector A, which in turn presses the springs 166 and 152 into contact, thus delivering` aground impulse to the rotary line conductor 181, as before, and as a result operating the private magnet 137 at the connector E. Thusfope'rating the private magnet 137 after the side switch G is in second position pro-v duces one of two results, namely the estab-y lishment of inal'connections with the desired line, ory the' busy-release of the connector switch E. "It will first be considered that the line is"'notbusyV and that' the private switch G 'to third position, placing the trunk conductors'182 and 181 in connection lwith the normal conductors 217 and 218. The

-nornial conductor 217 and the trunk conl ductor 182 are `connected through the side switch wiper 202, contact point 220,'conductor 221 and vertical line wiper 128'; and the normall conductor 218 and the rotary trunk conductor 181 are coimected through the side switch wiper 214, contact point 222, 100 conductor 223 and rotary line wiper 129. l-t will he noticed that when the sidel switch wiper 224 of the side switch G at the connector E passes into engagement with the contact point 225 the private trunkrelay a is energized in series with the private magnet 137 of the connector E, through the following circuit: from ground G9 at the ser lector side switch F to contact point 183,

side switch wiper 105, conductor 184, auXil-'v 110 i iary relay 124, private wiper 98, private trunk relay a', private trunk conductor 181, side switch wiper 224 of the connector E, contact point 225,conductor 227 to the private mag'- net 137, thence to the battery lead 204, and

springs 192 and 191 disengage, the line 125' switching relay 123 denergizes, restoring connection between the vertical trunk conductor 182 and the rotary trunk conductor 89, through the condenser 121 and through the line switching relay springs 194 and 130 195. It will be noticedl thattheauxiliagly relay 124 isstill supplied with current that flows throughv the private trunk relay a', and

tln'ough'the'private magnet 137 of ,the connector E;"but the aggregateresistances of l'tliesaid coils @fand 137 are sufficiently great to vpermit the springs which Athe auxiliary relay 124 controls to be restored, as eX-.

plained. Not only does the private trunk vrelay aeuergize in thelcirpuit .that has beenk descr1bed,vbut thelprivate magnet l1.37 also energizes,- causing the private magnet sprmgs..

223,' 20,9fand; 208,130 separate, andthe springs 208 '229. and 230 to engage( It will heino- Yticed jthat i the 4 priyate `wiper, .130, is directly connected. with the side switch Wiper 269,.

which side. switch: Wiper, upon passing to third. position, engagesl the .grounded con-5 tactpoin't'QTO. Therefore, whenconnection. .is maden-"ith a, desired line a` guarding. p01. tentialffroni .ground G .appears at fthe, ,prg-i, YatefA uiper '130. and, therefore, at..A .theprif vate noriinalronductor .219 and atall'rn'ultif ple',priv 'atejbarik contacts connectedtheneto,

,.lfo", rpfltectiirg.l the seized 4lille, againsti inter-f ference.

pears.;

crgizingthe relay 271 is two-'toldfnamely to remove the normal short-circu it `estab..

lished'through the cut-off relay springs 27 4 andj25,.and to .disconnect the trip magnet 276.'.fronithe said springs 274 and 275,.for preventing'the energizationof .the trip magnet .27.6 assoon as fthe.potentialior provid-,1. ing thecalllng subscrlbers line with talking' battery current. appears at-the normal confy ductors 217 and218. The vcut-oil relay;.271 is vdesigned to act veryv quickly-in fact,

much more quickly than the trip magnet. 276, lin order. to .accomplish the purpose. lstated. The path of the current through said .relay .271 may be. traced from ground G14 v atthe connector .side switch G to thev contaetfxpoint270, thence to the side switch wiper269, conductor 272, .private Wiper 130, private normal conductor 219 to the .cutolf relay 271,'and through said relay tothe battery lead 204, thence through battery B? to 4ground G2. After connection is established with the desired lcalled subscriber,

- the calling subscriber at substation C presses. hissignaling .button 31, carrying the sprung. 32 onto Ithe .grounded j contact 34, v'grounding the. verticalz line conductor 94y lfrom vthev sub-V d G3 .through the ground...

station groun .springs ,2l and .24. .to the conductor. .140,y

thencev to the Contact Vpoint34, through lthe spring 32, and. through the .springs 29 and.

28.tothe .verticalfline conductor .94.` Since the'lineswitching.relay 123 at theselectory .eratoiz Springsfl-l and il ssnalinsreulrentf tethaefilled'Subsrbersf' 1ine...0re1 ther felleuls .pursuits imm. the ringer. genereterflwrlilfthe Springs .1.14 and .8.5 llrthnsetethe srcleewithrwipef 10?, een- .tet peint .Qmeondnetr ,wiper 202, vertical,l trunk A .is .now denergi'zechas eXplained,. ground- 65 .ingthe 'vertical .line conductor-..94 .energizes thejyerticalline relay y99..`an,d thej dilerenl tial ,relay 117, with the result ,that Ithefringer. .relay 110. .energized lby, a flow. from ground- .G7- hreush. .the Springs-.152 7.0 4.and 15.1, andthroughi theflineswitching of lcurrent relay spnsaflfltank 498i; tol'fthe private springs .158. and :159, thence.; .over the: conductor 160 to the side switchwiper 1 04, con-v .110,..con ductor e233,..through @the ,dilferentialf relay, springs 234-;an31p235 x. (whichs .are .now-

in eontacwito -qthe 'through -lhattenf to.; ground.. .'lhe'.- f rlngelfrelanllm. .uren @grammer Switches. f 80 euriliaryfrer.. -layasnrnss .1.38 randfl artery line. .Wiper ductin- @223nr9ta1r/ line -sirerf.-.-l29,frotarye normal: scorrdueteu. (.215, .sr-1b.' lbers dietary; line. conductor-23.23,? lingen-ensuit .Sprmg `duetor' 221, iContactpoint .220, side switch conductor `,132, verticalwline. -W,i,per,...96, conductor 201,

line yswitchinfg...relay springs 4'1951 Sand, i.194, i100 conductor .244, 1contact,pr ,)r1 u s.245,V side swltch wiper..106, ripgerrelayfsprmgsll fand l1-16 y to the Aringer.,generatori .11.1. l' v he..su bscriber at substation; G,`ulp,0n y11e/airing, Ethe bell ,Y ring, removeshis -rfeceiwjerfl246-from the l105 switch-hook; 247, breakin'gthe ringer circuit'betveenthe springs,23 9 and .240, and'I closing the primary circuit'. ,'.betwe'en the springs :248 and 249,; when .the .switch-hook comprises .the 11o rises,- which, prilinaryrf circuit windings 250,. and ,-1251,iof.the,.backbr1d e coil-l2-2. Over thegsaidfpriinary.circuit't1e, transmitter. A25.2 ,of,the. called substation is provided. with. ,talking fbatter-y current,

,whiclrbattery current; also energizes the n.5 back-bridge rela-y 122: The. current inthe said .circuit. flow sffro1nfthe. side, switch ground .Gf-'at tl 1e ,..selector-l .AI to the side. switch: Wiper; 105, .thence ,to the :Winding 250 ,of the hackbr idge..relay;122.tothe con- 12o ductor'253,{ingerrelay. springs 112 and 113, Side Switch..wiper..l07, wntatrpint .236:,-conductor, 23T, auxiliaryl relay'springs l188 ,and`g.18,9..to .thefrrotarydinewiper 97,

thence4 tothe rotary..,tr.unk conductor .181, x25 l connector. 4 side. swgitch.4 Wiper. 214, .contact v point 2272,' conductorE ,rotary .line Wiper .129, rotary normal conductor'dv2'l'l8., rotary tactI point .231conduetop |232, iringer relay` vvground G'.

line conductor'238, primary winding 254 at the substation C', transmitter 252 through the springs 249 and 248 to the vertical line conductor 243, vertical normal conductor v217, vertical line wiper 128, conductor 221,

contact-'point 220, sideswitch 'Wiper 202, verticalv trunk conductor 182, vertical line wiper-96 at the selector A, conductor 201, line switching relay springs 195 and 194, conductor 244,-- contact point 245, side switch wiper 106 to the winding 251 of the backbridge relay 122, thence tothe differential relay .springs 255 and 235 to the batter'y lead 146,and through battery B to When the back-bridge relay 122 energizes, the sprin 164 is carried onto the spring 256, where y the calling subscriber is -in-'turn provided with talking battery currentfor the transmitter 8. The circuit over which this current is supplied extends from ground Go at the selector A to the side switch wiper 105, thence to the conductor 257, back-bridge 'relay springs 25,6.itnd1164t0 the winding 118 of the differential relay.117, rotary relay 100, rotary trunk conductor 89, line switch bank springs 57 #and 56 tother'otary'fline yconductor 95,

thence throughfthe primary winding l'land transmitter '-8 zandythrough 'theprimary springs 29 .and 28 vtothe verticalv line conductor'94, line switch bank springs. 54 and 55, vertical. trunk conductor 88, vertical lme relay 99,-'Winding 119 of the differential re-v lay 117 -to the battery lead 146, and through battery ,-Bfto. ground G. i The subscribers will, of course, be able to communicate with each-other over the circuits throu h which the. said talking current flows', Whic 1 circuits areinductively connected by the condensers 120 and 121, as shown in Figs. 1 and 4. T he talking circuits are indicated by the heavily marked lines. Of course, the voice-currents that pass through the primary windings 11 and 254 at the substations are induced in the secondary windings 12 and 258, which windings {are in .series With the receivers 2 and 246. After the two subscribers are throu h talking, and if the called subscriber shou d hang up his lreceiver first, the energizing circuit that has been described, which comprises the transmitter 252 and the backbridge relay 122 at the selector A, is broken. The relay 122, of course, denergizes and the springs 25.6 and 164, separate, and in turn the talking current for the transmitter 8 of the called subscriber is out ott', and whenthe spring 165 rengages the spring 164 the rotary line relay 100 and thewinding 118 of the dierential relay 117 are again connected with the non-grounded terminrl of battery B. The.' talking current having been cut 0H, if the Calling subscriber thenjhangs up his receiver hc grounds the vertical and rotary line conductors 94 and 95, thus simultaneously energizing the vertical and rotary line relays 99 and 100 of the selector A, and also the diierential relay 117.

The release of the switches occurs when the current through the said relays 99 and 100 and through the diii'erential relay 117 flows from substation ground G3 through the ground springs 21 and 24 tothe release spring 37, thence through the release springs relay 117 presses the springs 234 'and 235,

together. The vcurrent in Athis circuit flows from ground G12 tothe relay 122, trunk release springs 259 and '260 to fthe release magnet 109, thence'throughthe diii'erential relay. springs 234 and 235'to the battery lead 146, andthrough 'battery B to ground G. Therelease magnet 109, upon'energizing, attracts its armature 261, which latter kicks the double'dog 262y into normalposition, depriving the switch shaft 68 -ot' its support and rotating the side switch F into normal position, in the manner fully described in said connector. patent.v Then the switch shaft and side switch of the selector A are thus restored, the energizing circuit that has been previously described for the priva-te trunk relay a and the private magnet 137 or' the connector E is broken. Of course, the auxiliary relay 124 does not energize when the springs 185 and 186 of the relay a. rengage, because the side switch wiper 105 of the selector A has been restored to first position, and consequently neither does the line switching relay 123 energize; but as soon as the private magnet 137 of the connector E deenergizes, the springs 228 and 209 come into Contact, permitting a flow of current to pass through the release magnet 138 from the side switch ground G13 to the contact point 263, side switch wiper 264, conductor 265, private springs 228 and 209, conductor 210, side switch wiper 211, Contact point 266 to the release magnet 138, thence through said magnet to the battery lead 204, and through battery B2 to ground G2. The release magnet 138 then attracts its armature 267, which strikes the double dog 268, rotating the latter and depriving the switch shaft. 127 of its support and restoring the side switch G to normal position. lVlien the plunger arm 42, putting the latter in.r

springs 35, 36 and 37V do separate, the line. relays 99 .and .100', together with the dif-- ferential relay 117 of the selec-tor A, ide- .the switch' shaft 127 srestore'd the line' wipers 128 andy 129 brealrff connection with the .sl'ibscribers normal conductors v217 and 218, and the private Wiper 1810 disen'gages* from the private normal conductor 219. .When the connector switch shaft 127 is released, as. already explained, and When the privat-e Wiper 130 leaves theprivatenormalf'f conductor .219, th'e energizing circuit for the cut-ott1 relay'271 of the line .switch Xus broken', restoring-the said switch to the control ot' .the substation #220. At the saine time that the release magnet `109 of the selector A energizes, the release relay 1221' alsoenergizes, rbeing 1n the Vsame circuit; i

and as a result the springs 277 and 278 are pressed intol engagement, with the further result .that the' release .magnet 45'0t the lrne switch B' is energized by a flow orf current i from ground G15 at the selector A through the said springs. 278 and 277 to the trunk conductor? 90,` thence through the bankv spring`s59 and 5S of the switch-B (Fig. 3) to the release magnet 145,--andthrough the said magnet to the battery lead '146, thence E through battery 'B' toy ground GC Said.. release magnet 45,. upon energizing, attracts itsar1nature'46, andasa result the armature 49 .ot-the trip magnet 44 is raised So that 1 the terminal 163 o-said armature 49 latches readiness -tO"Wit-l1dra\iY the plunger 41, as soon as the release magnet denergizes, and when Ithe substation release springs 36 and 87 disengage; When' .the sald energize, and, ot course, the trunk release springs 259 and 260 and also the differential relay springs 234 and 235 separate,- destroying the energizing circuit for the release magnet 109 and the release relay 122, lVhen the release relay springs 27 S and 277 separate in turn, the energizing. circuitvfor the release magnet 45 of the 'line-switch B (Fig. 3) is cut olf, and the said mag.l

net denergizes, permitting the retracting spring' 48 to Withdraw the'plunger 41 from the bank tern'nnal J and bring 1t into' engagement 1with the plunger shaft 62. It

will be noticed by glancing at Figs. l and 3 that the ground potential that energizes the release magnet 45 of the line switch A nentra-lizes the; non-grounded potential that normally exists at the master switch bank contact 82 While the terminal J is busy, and it might appear that the reversal of said potential would cause some .trouble with .the propulsion of the master sWitcli.D, in the event that the wiper 74 should come to rest on the Contact point 82 While the said contact S2 is thus grounded; but to meet such a condition the differential relay 71 is provided with a second Winding 278a Which 1 ,esame is permanently connectedf with `the non'- grounded terminzliotzbatterv iB/.w lt Wil-l be evident, therefore, 'that' Whether y'negative or .positive potcnti'als'enist atiialny offthe'- master. switch :banlr contacts r u, the :differs thigl the' Winding'7 278%; depending upon which potential' is found by: the Wiper' 74;,

It will .b"u1rderstood, 3er-course, th'atwt'h'e grolnidvl potential' fat: the' masten switch' -b ank K 'will ordinarily appeal" there only 'durey inglzthe-.intertal' 01tthe release, lwhich' ratheiishlort.:.r After-the release' occurs', as described-,be switches-are la-l'l restored to' .their normal positions; ready vto be used bv any otherfs'ubseriber. f Itiit should happen tlrat-th'el calling-subscriber releases before the called `subseriber-thatf'?is, s before the' talking battery feurrentiis removed from the line-the -f apparatus I l operates a I trit'e' differently'. i Fori eainple', if they subscriber atfsub'tation' ffC 'g'ilolmdsw his 'ertical land ergizedgthe'spni'ri'g 164 engaged the' Grounded for reasons tliat'flaye already -been explaii'ied'.

ll-henthe-differential? relay springs 2.35 and 255 separate, thebaclr-ibridge relay 122 is deenergiz'ed and the callle'd. subscribers Iline is deprived of Atalking?battery current when the springs164 and 256v sepa-rate, While' the inside' terminal of the rotary side ofthe line is lrestored to normal engagement with the non-groundedy terminal of battery B as soon as the spring 1564 4afd-"varices enough to reiigage the spring 1.165.` The' "rotary line relay-'10( ),'thereore, renergizes by a flow` of current in the reverse' ldirection, and the difere'nti'al relay l117 is further strengthened bythe reverse flop through the' Winding 118. The' renergizationof the rotary line 'relay Acauses tlievrengagement"of the trunk release springs 259 and 260; and since the differentiall relay 1-17 has inthe :meantime advanced the-spring 235 .into engagement with t'l1espr1ng-231, there occurs the enerrelay -1222 The succeeding steps in therehave' already been-explained. It. the` called ot the selector A, side switch wiper 107, ringer relay springs113 and 112, conductor f. 253, -condenser 120, vertical trunk conductor g'ization of the vertical line relay 99, of the -f `frotary line relay 100, and ol. the ditl'erential relay 117, which, as 4has been previously i Allpointed out, establishes anenergizingre-A rlease circuit through; thefrele'ase magnet 109 of the selector A; andzthrough v the a release v l L Alease are,po course', the same' as .those which 488,2line switch bankv springs 55 and 54:, vertical line conductorv 94,through the. primary winding 11 atthe substation C to the rotary line conductor A95,l thence to the'line switch bank springs 56 and- 57 to ,the rotary trunk conductor89, rotaryline'relay 100, wind- 1 ing 118 of thedifl'erential relay 117, back-5f `bridge relay springs -164 and' 165 tol the subscriber-s line had been busyf the, conv.

.f vnector side switchG wouldnot have passed A tol third position, as already stated, but to the -contrary the said connector would' have been vreleased and the -side switch would have been thrust into first position. :Taking up .the call at thatl stage, when thel calling subscriber grounds Ithe rotary line conductor 95 at the end of the-lastzdigit naught,'as has been pointed out, the rotary lin'e relay-:100

n ground impulse to the rotary. trunkfcon- .130 has, previousto this,been carried into -.engagement ywith a grounded contaetpoint;

of the -.selector A- energizesV and sends a vertical 1ine'relayl39 and the private magductorI 181 that :leads -to therconnectorE. A Y Thesaiddmpulseis .received by: the private .magnet 137- 'which upon; energizing, f :forces ,the privatel springs 229 and 230 into contact ybefore the side switch G has had time to trip to third position. The --private wiper consequently, since the' side switch Gis in second position, at the instant that the private springs 229 and230 engage, a'tlow ot current is. sent tlnough the release magnet 138 over the following circuit: from the grounded contact' point to the private wiper 130, thence tothe side switch wiper 269, contact point 279, conductor 280,` private springs'229 and 230,. conductor. 281 to-the release -magnet 138, thence to the-*battery signaling button 31, whereby the vertical 'lead 201, and through battery B2I `tog'round G2. The releasemagnet 138, ot course, attracts its' armature 267, restoring the side switch Gr and switch shaft 127.4 The subscriber at substation C, thinking that the connection has been established, presses the line conductor 94: is grounded. The effect of grounding-thel vertical line conductor at this'time is to energize the vertical 4line relay 139 at the connector E, thereby stepping up the shaft 127, as explained. The subscriber at substation .C then receives a busy-signal from the busy-signaling machine L (Fig 1)- that comprises the induc tion-coil282 which is providedvwith a primary winding 283^and a secondary -winding 284. The current passes romthe secondary winding 281, conductor :285, auxiliary relay1 springs 190 and 188 (bearing inmi-nd-that the relay 1211 is energized and in an operated position at thisv particular` time, as eX- plained) conductor .237, contact Ilpoint .236

battery lead 146 and back tothe coil'f284. The busy current is induced in the secondary winding 12,; ofthe induction-coil 10 at; the substation C, which current. then flows through the receiver 2, and which is, of course, heard by the subscriber. He then -tary -linerelays 99. Land 100 -an'd the Y diierential relay :117 ofthe seleeto'rlA; andwthe net 2137 lof.theconneetor -E are' alsoieneiw gized.:si1nultaneously -when',y the side switch G isfin first orsecond position,^closing an energizing circuit ,through thev connectorrelease magnet `138 extending .from\-gronnd 5G11. through.:the springs 205 la'nd206, pri-.. fvate magnet-138 to the batterylead==204, thence through'battery B2v to Vground1C-lf2.

The. release magnet,- 138, upon energizing, operates asbefore -to restore-thefconnector Vswitch E. The -vertical line 'relay 99;--and the rotary line relay of-theseleetor- A venergize simultaneously, whereby the release magnet 109 and the release relay 2122 of the said switch A are energized,V as previously explained, producing the 'release oli' the said switch and ofthe line switch B. Ot course, when the side switch F of the selector A passes to first position-the auxiliary relay 124, as well as the line switching relay 123, denergize; and when the substation releasesprings 35, 36 and 37.di's engage, all of the switching apparatus is fully restored, as explained.

In the selector A the various coils may be wound to 'any suit-able resistance, butithas beenv found that good results are obtained when the line relays 99 and 100 are of'one hundred ohms each; windings 118 and 119 of the diferentialrelay 117 two -hundred and fifty ohms each; windings of the backbridge relay 122 three hundred' and fifty i ohms each; line switching-relay 123 twentythree hundred ohms; auxiliary relay. 124:'

l one-half ohm; ringer relay 110 tive hundred -ohm private trunk conductor relay c-.siXty ohms; and in the connector E the line relay 139 ve hundred'ohms, and the private magnet 137 three hundred andI ifty'ohms. 11n

the ,line/switch' B-ithe insistance-ot' the release-magnet niay be-sixty ohms, the trip :magnet/i4 sixty ohms, and the cut-offrelay 143 mayl be -f-romi one;thousand"to one-thou- 3. A telephonevsystem comprising artem- .rporarily established 'talking circuit, means for dividing sai-d 'circuit'. into i-nductively connected sections, automatic switches in 5. sand'- three. hundred-ohms "said circuit; means for repeating or relaying 70 Fromthe'foregoing'f. it willbe -seen'that l switch-operatingimpulsesI from one section vprovide selectors wwhich. 4have four unc- -'of' said' circuit -to another, and meansl for tionsftoswitpthe selectio'n of' idle :trunkilsupplying talking current through one of lines, xthe relayingior'repeatingof -switchsaid.. switchesotherithan the final one, to

y y operating electrical 'impulses tol other -both. ends otsaiditalking circuit, said secondV 75 -switches, the. bridgingfof a source o'iingl'means including za. relay, saidrelay included 'ing-current-across they trunk-lines which vinlthe path ofi-*said current.

havev been extendedzfto4 tlieculled subsoifib- 4.' A telephone-system, :means for estabersliiicsynndftlic controlling-of thesupply A l-ishing wtalkingcircuit comprising trunk lof'talkingcurrent-from the common-batteryfilmes,ian:autoinaticftrunk selector providedA 180 -toth'eftemporarily established talking-cirwith means'for .-relavingor repeating imcuit between .ceiling-and called subscribers. r 'pulscstoany selectedtiunk line, and means It'willfleiundcrstooih of course, 'ftlia't the foi=supp'lying ringing. or `signaling current -con-nectors E can berlesscinniunber than the itftliouglr 'said selector to any selected trunk :lfzcrtotal number o'subscribersilines, `and that llineQ--a motor .inagnetfor said selector, said 185 the .selectors A cansber-the `salines in.numler I' magnet -jcontrolled inver. circuits excluding 'ras fthe said.y connectors; 1Wlierielzly-the vautosaidi talking circuit. r I

fHinatic-trunking througlrfthe ekcllan'ge isicon`1 2.15. A telephoneg'systeln, means for estabpducted. on;aaercentge'basisu 'Ehe'subflishingfn, talking ycircuit comprising trunk f=-'scriber`sl line oi' individual sivitehe's'iB .Will, limes., an-uutor'natic trunk selector provided-90 Tof course, bethesmeinnumber:asthelslrbiwithimeansorrelaying or Irematiifig ini- 'scribers telephone li-nesfand 4thellatter can A.pulsesto:any.selectedtrunk line, means for be'dividedi intoilgroups, nr'the'iwell-lmown 'supplying *iiinging -or signalingcurrent n mannenV vlForma.larger exchangeztheaplau through-fsidifselctor :teeny selected trunk ""'30 l'tLlS CM1'lJGnCrcaScdnirden"toiproiflleline, and imeansffor-supplying. talking cur- 95 twoi'ormoreselectors between the'findividual I ,pent-through gaidiselector to my Selected 'switchesrand the connect-ors-stilmtiiSdmSy, .trunkline',` amdtor magnetfor said selector`r Sre-Sito' enableicadhcallingfsubsebr tOfil'llf. 'saiimagnetcontrolled over circuits cXcludploy two or-"more selectorsifor extending ing-Said walking circuit,

"-135 connection to an idle-connector."l In such l6, A districttelephone system comprising 100 case itfWill .also bc undel'StOOflthab the Calliva-central` station.' sub-'central stations. suhving SUlOSCX'lOCI -WlllollyluplOY/f Ollfftlw scribersltelephoneflines :terminating at said SGRC/tofs 0f the WPC indicated fnglalS sub-central stations, trunk lines between the Vlllme- Otllel'vlSGlCCl'S"TG--IIGCGSSMY ill centritl' stution'fand Athesub-central stations` 40 order to cxtendfthe .connection candieof'the {mnnegms at theicntml Smtjcn for-supply- 105 'regular or ordinary type. i '-fingftalkng-current over the trunk lines to I W'luit -Clflim 21S IUYIHVSHOIL S "thefcallin-gf and called telephone lines ler- 1. A telephone system comprising .at `60uminatiug'at tliesub-centrnl stations. Demol', il' Sdtm' 1L talk-111g Circ-uit includ 7. Ai felelihonc svstem comprising a main ing the Selectm' dnd Gonnectrv *l 'Plulally 0f centrel Station. lslib-central stations. trunk 11(l bilielv'-QS, means 5.11 the Selectorv OI' bridging -linesfbetween thenia-in' central station and (me bat-i813 {LCPOSS th Circ/it m-Sulplytu- Ithe 'sub-mutral stations. subscribers telolllg Cill'lni) t() lGOtll 'llClS thereof, C-lICllltS fOl' phone, tlmiinating nl'. the gnlyQQp-il operating the connector from another ci? Stations, n, gor'of ringing @1u-rent, t tha Sllfl bttl'leS {Llld .t lllllelly OI COII'II'Ol- (intlgrl-statign, and rnganff, at, the Coniyal 115 ling the setting'uooperation of saidselector, ysgi-,ation:for bridging said source of ringing Said WM5" included ill the Path '0f Said CUI 4-fj,iirrent12x-Crosszuiy trunk line b v which cmi- I'GH- I nection -lias beenI extended to a calledA suh- Q. AAL- telepllOllG SySlelllOmplSlng b6111- -Srbel'lg-'telephone line;

porarily established talking circuitbetween I f 38. lAAAtelephone*system comprising a. trunk 120 5L vCalling and d- Cufl-uedsllbscl'ibls lille, ill-S0- li-ne, alcaliedtelephone line. autonniticmeans lector and a conncctoriu said circuit,:;said fen-endingConnection' from the trunk selector provided withA ineansolf conrnl- -flinetfthe-ftel'eplione line, a. source oi' ringling vthe operations of tlic'COnrlcCi/Or-,anfl-MSO ving current, fand means under. tlic'control oi'j 60.y with 'means wherebyit ine-y be foilierated-to U thecallingsubscriber afterthc-connection is 125 extend the talking circuit'froin thecalling f completed'for bridging said source of ring` .subscriber'ltotlie-connectoibefore sai'diconf-'ing loi'lrrent across-'the trunk line. where j.' nector is operated, and'niensjfor supplying ringingfcurrentislsent 'over the' entire trunk talking current through the selector to 5both linet'o signal thecalle'd subscriber.

endsof the talking circuit.- i f- '9;1A`fte'lephone system comprising tele' 130 trunking means ,for trunking callingtelef phone lines into connection with 4-idle switches, and means for supplying-'talking current through said automatic trunking :L

phone'lines, suitableswitclies forextending f connection to said:- telephone lines, automatic o'tsaid' llines, said connector provided -with terminals of Said'lines arranged ina-plumeans to the telephone lines, the operation I switchhook. i;V f.,

f1.0. Ateleph'one `system comprisingztelerality' of levels; means for selecting 'a terminalin any'leveha single line relay and 1a private 'magnet/,connected directly to the trunk linegi-byfavhich operations of the oonynectorarev controlled,'1and a side sivitch op-v ot; saidrautolnatlc trunking meansl being r lnitiated vwhen' `the .subscriber '.fraises'-'h 1s erated'rby'saidI private magnet.

phonelines, suitable 1'svvitchesifo'r 'extending connection lto Ysaidf telephone lines',r auto mati'cftrunking means lfor trunking calling telephone lines into connection :with idle switches;and meanssfor supplying ringing .f'current through the vsaid `'trlmlm'ig :means -fto the calledtelephone .linesg'thefoperati'on of said automaticitrunkingme'ans being'i'ni- 11; -In a f telephone*v system, fthe 'combination of f an auxiliary relay, 'aline switching 1relay, a "rotary line Wiper, laverticalrtrunk conductor, :means by v'vhich the auxiliary re- 12. fI-n a telephone system 'the combinationi 4of a line switching J relay, a pair'l 'of springs, a pair of trunk conductorsg'lmeans 'by which said relayisfadapted'to open-one side -of the line, means vbyvvhi'cli L'the 4said 'relay is adapted to switch -said'springsldi- -rectly into connection with the said conductors, and aside switch, said relay adapted A-for repeating or relaying 'felectrical-y impulses to the trunk line 'after the' side switch passes to third -position.f A 1 'l 13. ln a telephone system, subscribers lines,`a first trunk line common to said lines,

lneans for automatically extending connection to said second trunk l1ne,a relay 1nd1- vidual to said first trunk' linefcontrol'lin'g'the line` and a circuit through said automatic mea-ns controlled by said relay.

Y 15. A telephone 'system comprising-telephone lines, a'connector for-automatically seizing and extending connection to any one the subscriber raises 'his sivitchtrunkV line, arid'. an electromagnet in said aufinon tb said subscribers lines for lextending .iconnection to an :idlerone 'of said trunk lines, awlrelay -lorfthe third conductor" of each ';tomatic means-adapted'to 'be controlled by any one of said relays.

l 17.A" telephone system'comprising a plu- -ra'lity of-jthree-'co'nductor trunk lines, automatic means; for" extending vconnection -to an ,'ldle"one'off-said'trunklines. a relay for the *thirdconductor of 'each trunk line, means 'for energizlngv saidfrel'ays, an :electromagnet included in saidwlutomatic means,a'nd 'means i i f irlf-.yate telephone f 'systems i comprising g a threeiconductoI-trunk line, automatic means .tween thefrotary line Wiper and the yertical f" 'trunk conductor; J3-.1

fori extendings connection i to's'aid'` Itrunk line, automatic means for extending connection ffromtheotherend of said tr'unk line, relays in f'both' said` 'automatic means' 'adaptedv to reljniain lenergiz'ed f during conversation o'ver fthe trunk `ilinef," adfan energizing circuit including said f -relays f and 'third' conductor of- "flines',a plurality of ltrunk lines common to -s'al'd lines,- automatic'fmeans'for' selecting an 'idle one 4of sa1d` trunklines, a relay allotted to eachtru'nk li'ne, said relaysassociated' with' vthc-trunkline terminals which are adapted tto-be seized bysaid' automatic l'neansgmeans a second trunk line having three conductors,

l:for keepingthe'talking circuit between said line andtrunk open, and means controlled by the relay associated with said idle trunk '-f ing purposes for vrestoring said talking circuit tfor talk- 20. In a" telephone system, subscribers lines, a plurality of trunk lines common to said subscribers lines, automatic' means for selecting idle' trnnklines. la relay allotted to one end of each trunk line, and switching meansat the other end of said trunk lines controlled by said relays, means for keeping "the talking: circuit between said line and storing poses.

trunk open, andmeans controlled by the re- A'lay associated'-with said idle trunk for rcsaid talking circuit for talking pur- 21. In a telephone system,` a private magnet, a battery, a trunk-line having a trunk conductor -excluded from the talking cir'- cuit` and a relay adapted to remain energized in series with the private magnet and 

